Efficient dye-sensitized charge separation in a wide-band-gap p-n heterojunction

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Abstract
We report the fabrication and performance of a dye‐sensitized p‐n heterojunction formed from a planar interface between two wide‐band‐gap semiconductors, n‐TiO2 and p‐CuSCN, which contains an intervening monolayer of a sulforhodamine B dye. When exposed to visible light, the photoexcited dye molecules transfer electrons to the n‐TiO2 and holes to the p‐CuSCN. The absorbed‐photon‐to‐current efficiency (APCE) is ≳70% and the open circuit voltage is ≊500 mV. This heterojunction is the solid‐state analog of the dye‐sensitized photoelectrochemical interfaces used in photography and photovoltaics. The high quantum efficiency and voltage show that it is possible to simultaneously optimize both the dye/n‐type and dye/p‐type interface for efficient forward charge injection and slow charge combination in a solid‐state device.